SHP-1, a protein-tyrosine phosphatase with two Src homology 2 (SH2) domains, is a regulator of various intracellular signaling molecules, such as signal transducer and activator of transcription 3 (STAT3), KIT, CD22, CD5, CD72, SHPS-1, TIMP (metalloproteinases), CDK2, p27, SRC, ZAP70, IL-10, NF-κB, Lck, 3BP2, Lyn and cyclin D1.
STAT3 is a transcription factor which regulates cell growth and survival by modulating the expression of target genes. It acts as an oncogene which is constitutively active in many cancers including liver, lung, head and neck, prostate, and breast as well as myeloma and leukemia. A key regulator of STAT3 activity is SHP-1. From a mechanistic perspective, SHP-1 exhibits protein phosphatase activity which reduces the level of Phospho-STAT3 (P-STAT) and subsequently blocks the dimerization of P-STAT3. Therefore, expression of target genes, such as cyclin D1 and survivin transcribed by STAT3, is significantly reduced. In addition, studies of SHP-1 protein and SHP-1 mRNA showed that expression level of SHP-1 was low in most cancer cells; and genetic increase in SHP-1 in cancer cells resulted in the suppression of cell growth, suggesting that the SHP-1 gene acts as a tumor suppressor. From the drug discovery point of view, development of a small molecule which can reduce P-STAT3 and increase SHP-1 level is a promising direction for cancer therapy. SHP-1 also play an important role in bone remodeling, a process of bone-forming osteoblasts and bone-resorbing osteoclasts. Loss function of SHP-1 results in osteoclast and eventually leads to osteoporosis. Therefore, enhancement of SHP-1 activity might be a direction for osteoporosis patient. In addition, increase of SHP-1 is benefit for the macrophages of multiple sclerosis patients